Traffic signs are commonly used to convey road use regulations and road current conditions for vehicles (including automobiles or “cars”), bicyclists, pedestrians, etc. Fixed, printed traffic signs are frequently posted to define exceptions to default regulations and usage of roadways, for example to allow or prohibit parking on certain roadways, or turning left or right in certain areas to control traffic flow, or create an exception to current laws (such as preventing “right turns on red” at a certain intersection that would otherwise be permitted by applicable traffic laws). Often such signs include additional conditions that must be met in order for the communicated restrictions and usage rules to apply, such as prohibiting parking or requiring payment to parking meter devices only during specified time periods (hours of the day or days of the month or week), restricting parking during the occurrence of certain conditions (for example, prohibiting parking when snow fall accumulation exceeds two inches), or changing one way or two-way traffic allocations based on time of day (for example, during posted rush hours only).
Active signs may change messages displayed thereon via direct programming by operators or automated applications, or in response to timed programs, for example to automatically invert direction marker during rush hour times within a large city. Active signs may include electronic displays that use a variety of technologies, including illuminated liquid crystal display (LCD), light emitting diode (LED), video projection and monitor displays, and non-illuminated electronic ink displays that rely on natural or external light sources for illumination. Active signs may revise information content displayed to a car driver to convey different traffic rules, estimated commuting times and traffic detours and disruptions.